It is known in the prior art to employ permanent magnets to remove ferrous metal from a flow of material such as granular material, broken material including rubble, and waste material including for example, organic material for use in bio-mass energy reclamation. Typically, a flow of material is conveyed on an endless conveyer and the permanent magnets are positioned relative to the conveyer, and relative to the flow of material thereon, so as to attract, and retain against the permanent magnets or their housing, any ferrous materials passing in proximity to the magnets. However, it often proves difficult and time consuming to clean the ferrous materials adhered to the permanent magnets due to the strong attractive force of the magnets as the cleaning of the ferrous materials from the magnet is typically done by a worker. Consequently it is also known in the prior art to use electro-magnets instead of permanent magnets, so that electro-magnets maybe de-energized when it is desired to remove the adhered collection of ferrous metals. However, use of electro-magnets is relatively expensive, and requires a powered source of energy for the electromagnet.
Consequently, there exists a need for a device which enables the cleaning of ferrous metals on the face of permanent magnet housing, and in particular, such a cleaning device which requires little or no additional external power source for operation.
In the prior art, Applicant is aware of PCT international patent application no. PCT/US99/23383 which published on Oct. 5, 2000, under publication number WO 00/58186 entitled: non-continuous system for automatic self-cleaning of permanent magnets or electro magnets. That patent application discloses a non-continuous, self-cleaning or automatic cleaning system for magnets consisting of a non-magnetic sweeper, where the sweeper is kept in place and allows free movement by means of guide bearings on the respective sides of a plate. The movement of the sweeper is taught to be achieved by mechanical or impact, pneumatic or hydraulic systems and electric motors. The sweeper has a flat face which moves forwardly and strikes iron particles adhering to the magnetic surface so as to expel the particles in the same direction as the forward motion of the sweeper.